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end"></span></button><!----></section></li></ul><!--[--><!----><!--]--></aside><!--[--><main id="main-content" class="vp-page"><!--[--><!--[--><!----><!--]--><!----><nav class="vp-breadcrumb disable"></nav><div class="vp-page-title"><h1><!---->Redisson看门狗机制</h1><div class="page-info"><span class="page-author-info" aria-label="作者🖊" data-balloon-pos="down"><svg xmlns="http://www.w3.org/2000/svg" class="icon author-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="author icon"><path d="M649.6 633.6c86.4-48 147.2-144 147.2-249.6 0-160-128-288-288-288s-288 128-288 288c0 108.8 57.6 201.6 147.2 249.6-121.6 48-214.4 153.6-240 288-3.2 9.6 0 19.2 6.4 25.6 3.2 9.6 12.8 12.8 22.4 12.8h704c9.6 0 19.2-3.2 25.6-12.8 6.4-6.4 9.6-16 6.4-25.6-25.6-134.4-121.6-240-243.2-288z"></path></svg><span><span class="page-author-item">小刘Learning</span></span><span property="author" content="小刘Learning"></span></span><!----><span class="page-date-info" aria-label="写作日期📅" data-balloon-pos="down"><svg xmlns="http://www.w3.org/2000/svg" class="icon calendar-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="calendar icon"><path d="M716.4 110.137c0-18.753-14.72-33.473-33.472-33.473-18.753 0-33.473 14.72-33.473 33.473v33.473h66.993v-33.473zm-334.87 0c0-18.753-14.72-33.473-33.473-33.473s-33.52 14.72-33.52 33.473v33.473h66.993v-33.473zm468.81 33.52H716.4v100.465c0 18.753-14.72 33.473-33.472 33.473a33.145 33.145 0 01-33.473-33.473V143.657H381.53v100.465c0 18.753-14.72 33.473-33.473 33.473a33.145 33.145 0 01-33.473-33.473V143.657H180.6A134.314 134.314 0 0046.66 277.595v535.756A134.314 134.314 0 00180.6 947.289h669.74a134.36 134.36 0 00133.94-133.938V277.595a134.314 134.314 0 00-133.94-133.938zm33.473 267.877H147.126a33.145 33.145 0 01-33.473-33.473c0-18.752 14.72-33.473 33.473-33.473h736.687c18.752 0 33.472 14.72 33.472 33.473a33.145 33.145 0 01-33.472 33.473z"></path></svg><span><!----></span><meta property="datePublished" content="2024-10-12T11:34:40.000Z"></span><!----><span class="page-reading-time-info" aria-label="阅读时间⌛" data-balloon-pos="down"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="timer icon"><path d="M799.387 122.15c4.402-2.978 7.38-7.897 7.38-13.463v-1.165c0-8.933-7.38-16.312-16.312-16.312H256.33c-8.933 0-16.311 7.38-16.311 16.312v1.165c0 5.825 2.977 10.874 7.637 13.592 4.143 194.44 97.22 354.963 220.201 392.763-122.204 37.542-214.893 196.511-220.2 389.397-4.661 5.049-7.638 11.651-7.638 19.03v5.825h566.49v-5.825c0-7.379-2.849-13.981-7.509-18.9-5.049-193.016-97.867-351.985-220.2-389.527 123.24-37.67 216.446-198.453 220.588-392.892zM531.16 450.445v352.632c117.674 1.553 211.787 40.778 211.787 88.676H304.097c0-48.286 95.149-87.382 213.728-88.676V450.445c-93.077-3.107-167.901-81.297-167.901-177.093 0-8.803 6.99-15.793 15.793-15.793 8.803 0 15.794 6.99 15.794 15.793 0 80.261 63.69 145.635 142.01 145.635s142.011-65.374 142.011-145.635c0-8.803 6.99-15.793 15.794-15.793s15.793 6.99 15.793 15.793c0 95.019-73.789 172.82-165.96 177.093z"></path></svg><span>大约 4 分钟</span><meta property="timeRequired" content="PT4M"></span><!----><!----></div><hr></div><div class="toc-place-holder"><aside id="toc"><!--[--><!----><!--]--><div class="toc-header">此页内容<button type="button" class="print-button" title="打印"><svg xmlns="http://www.w3.org/2000/svg" class="icon print-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="print icon"><path d="M819.2 364.8h-44.8V128c0-17.067-14.933-32-32-32H281.6c-17.067 0-32 14.933-32 32v236.8h-44.8C145.067 364.8 96 413.867 96 473.6v192c0 59.733 49.067 108.8 108.8 108.8h44.8V896c0 17.067 14.933 32 32 32h460.8c17.067 0 32-14.933 32-32V774.4h44.8c59.733 0 108.8-49.067 108.8-108.8v-192c0-59.733-49.067-108.8-108.8-108.8zM313.6 160h396.8v204.8H313.6V160zm396.8 704H313.6V620.8h396.8V864zM864 665.6c0 25.6-19.2 44.8-44.8 44.8h-44.8V588.8c0-17.067-14.933-32-32-32H281.6c-17.067 0-32 14.933-32 32v121.6h-44.8c-25.6 0-44.8-19.2-44.8-44.8v-192c0-25.6 19.2-44.8 44.8-44.8h614.4c25.6 0 44.8 19.2 44.8 44.8v192z"></path></svg></button></div><div class="toc-wrapper"><ul class="toc-list"><!--[--><li class="toc-item"><a class="vp-link toc-link level2 toc-link level2" href="#看门狗机制">看门狗机制</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level2 toc-link level2" href="#watch-dog的自动延期机制">Watch Dog的自动延期机制</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level2 toc-link level2" href="#源码分析">源码分析</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level2 toc-link level2" href="#总结">总结</a></li><!----><!--]--></ul><div class="toc-marker" style="top:-1.7rem;"></div></div><!--[--><!----><!--]--></aside></div><!--[--><!----><!--]--><div class="theme-hope-content"><h2 id="看门狗机制" tabindex="-1"><a class="header-anchor" href="#看门狗机制" aria-hidden="true">#</a> 看门狗机制</h2><figure><img src="https://gitee.com/eddie-lucas/images/raw/master/img/816762-20210425105548419-1714180337.jpg" alt="" tabindex="0" loading="lazy"><figcaption></figcaption></figure><p>Redisson 锁的加锁机制如上图所示，线程去获取锁，获取成功则执行lua脚本，保存数据到redis数据库。如果获取失败: 一直通过while循环尝试获取锁(可自定义等待时间，超时后返回失败)，获取成功后，执行lua脚本，保存数据到redis数据库。Redisson提供的分布式锁是支持锁自动续期的，也就是说，如果线程仍旧没有执行完，那么redisson会自动给redis中的目标key延长超时时间，这在Redisson中称之为 Watch Dog 机制。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token comment">//几种加锁方式</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">test</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span><span class="token punctuation">{</span>
    <span class="token class-name">RLock</span> lock <span class="token operator">=</span> redissonClient<span class="token punctuation">.</span><span class="token function">getLock</span><span class="token punctuation">(</span><span class="token string">&quot;testLock&quot;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>    <span class="token comment">// 拿锁失败时会不停的重试</span>
    <span class="token comment">// 具有Watch Dog 自动延期机制 默认续30s 每隔30/3=10 秒续到30s</span>
    lock<span class="token punctuation">.</span><span class="token function">lock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">// 尝试拿锁10s后停止重试,返回false 具有Watch Dog 自动延期机制 默认续30s</span>
    <span class="token keyword">boolean</span> res1 <span class="token operator">=</span> lock<span class="token punctuation">.</span><span class="token function">tryLock</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">,</span> <span class="token class-name">TimeUnit</span><span class="token punctuation">.</span><span class="token constant">SECONDS</span><span class="token punctuation">)</span><span class="token punctuation">;</span> 
    <span class="token comment">// 没有Watch Dog ，10s后自动释放</span>
    lock<span class="token punctuation">.</span><span class="token function">lock</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">,</span> <span class="token class-name">TimeUnit</span><span class="token punctuation">.</span><span class="token constant">SECONDS</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">// 尝试拿锁100s后停止重试,返回false 没有Watch Dog ，10s后自动释放</span>
    <span class="token keyword">boolean</span> res2 <span class="token operator">=</span> lock<span class="token punctuation">.</span><span class="token function">tryLock</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">,</span> <span class="token class-name">TimeUnit</span><span class="token punctuation">.</span><span class="token constant">SECONDS</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">sleep</span><span class="token punctuation">(</span><span class="token number">40000L</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    lock<span class="token punctuation">.</span><span class="token function">unlock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="watch-dog的自动延期机制" tabindex="-1"><a class="header-anchor" href="#watch-dog的自动延期机制" aria-hidden="true">#</a> Watch Dog的自动延期机制</h2><p>如果拿到分布式锁的节点宕机，且这个锁正好处于锁住的状态时，会出现锁死的状态，为了避免这种情况的发生，锁都会设置一个过期时间。这样也存在一个问题，假如一个线程拿到了锁设置了30s超时，在30s后这个线程还没有执行完毕，锁超时释放了，就会导致问题，Redisson给出了自己的答案，就是 watch dog 自动延期机制 Redisson提供了一个监控锁的<strong>看门狗，它的作用是在Redisson实例被关闭前，不断的延长锁的有效期</strong>，也就是说，如果一个拿到锁的线程一直没有完成逻辑，那么看门狗会帮助线程不断的延长锁超时时间，锁不会因为超时而被释放 默认情况下，看门狗的续期时间是30s，也可以通过修改Config.lockWatchdogTimeout来另行指定。另外Redisson 还提供了可以指定leaseTime参数的加锁方法来指定加锁的时间。超过这个时间后锁便自动解开了，不会延长锁的有效期</p><h2 id="源码分析" tabindex="-1"><a class="header-anchor" href="#源码分析" aria-hidden="true">#</a> 源码分析</h2><ol><li><p>watchDog 只有在未显示指定加锁时间（leaseTime）时才会生效。<strong>（这点很重要）</strong></p></li><li><p>lockWatchdogTimeout设定的时间不要太小 ，比如我之前设置的是 100毫秒，由于网络直接导致加锁完后，watchdog去延期时，这个key在redis中已经被删除了</p></li></ol><p>在调用lock()时，会最终调用到tryAcquireAsync。调用链为：lock()-&gt;tryAcquire-&gt;tryAcquireAsync</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">private</span> <span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">T</span><span class="token punctuation">&gt;</span></span> <span class="token class-name">RFuture</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Long</span><span class="token punctuation">&gt;</span></span> <span class="token function">tryAcquireAsync</span><span class="token punctuation">(</span><span class="token keyword">long</span> waitTime<span class="token punctuation">,</span> <span class="token keyword">long</span> leaseTime<span class="token punctuation">,</span> <span class="token class-name">TimeUnit</span> unit<span class="token punctuation">,</span> <span class="token keyword">long</span> threadId<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token class-name">RFuture</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Long</span><span class="token punctuation">&gt;</span></span> ttlRemainingFuture<span class="token punctuation">;</span>
    <span class="token comment">//如果指定了加锁时间，会直接去加锁</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>leaseTime <span class="token operator">!=</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        ttlRemainingFuture <span class="token operator">=</span> <span class="token function">tryLockInnerAsync</span><span class="token punctuation">(</span>waitTime<span class="token punctuation">,</span> leaseTime<span class="token punctuation">,</span> unit<span class="token punctuation">,</span> threadId<span class="token punctuation">,</span> <span class="token class-name">RedisCommands</span><span class="token punctuation">.</span><span class="token constant">EVAL_LONG</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
        <span class="token comment">//没有指定加锁时间 会先进行加锁，并且默认时间就是 LockWatchdogTimeout的时间</span>
        <span class="token comment">//这个是异步操作 返回RFuture 类似netty中的future</span>
        ttlRemainingFuture <span class="token operator">=</span> <span class="token function">tryLockInnerAsync</span><span class="token punctuation">(</span>waitTime<span class="token punctuation">,</span> internalLockLeaseTime<span class="token punctuation">,</span>
                                               <span class="token class-name">TimeUnit</span><span class="token punctuation">.</span><span class="token constant">MILLISECONDS</span><span class="token punctuation">,</span> threadId<span class="token punctuation">,</span> <span class="token class-name">RedisCommands</span><span class="token punctuation">.</span><span class="token constant">EVAL_LONG</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token comment">//这里也是类似netty Future 的addListener，在future内容执行完成后执行</span>
    ttlRemainingFuture<span class="token punctuation">.</span><span class="token function">onComplete</span><span class="token punctuation">(</span><span class="token punctuation">(</span>ttlRemaining<span class="token punctuation">,</span> e<span class="token punctuation">)</span> <span class="token operator">-&gt;</span> <span class="token punctuation">{</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>e <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">return</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>

        <span class="token comment">// lock acquired</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>ttlRemaining <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token comment">// leaseTime不为-1时，不会自动延期</span>
            <span class="token keyword">if</span> <span class="token punctuation">(</span>leaseTime <span class="token operator">!=</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                internalLockLeaseTime <span class="token operator">=</span> unit<span class="token punctuation">.</span><span class="token function">toMillis</span><span class="token punctuation">(</span>leaseTime<span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
                <span class="token comment">//这里是定时执行 当前锁自动延期的动作,leaseTime为-1时，才会自动延期</span>
                <span class="token function">scheduleExpirationRenewal</span><span class="token punctuation">(</span>threadId<span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">return</span> ttlRemainingFuture<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><code>scheduleExpirationRenewal</code>中会调用<code>renewExpiration</code>。 这里可以看到是,启用了一个timeout定时，去执行延期动作</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">renewExpiration</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token class-name">ExpirationEntry</span> ee <span class="token operator">=</span> <span class="token constant">EXPIRATION_RENEWAL_MAP</span><span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token function">getEntryName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>ee <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">return</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token class-name">Timeout</span> task <span class="token operator">=</span> commandExecutor<span class="token punctuation">.</span><span class="token function">getConnectionManager</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">newTimeout</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">TimerTask</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token annotation punctuation">@Override</span>
        <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">run</span><span class="token punctuation">(</span><span class="token class-name">Timeout</span> timeout<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span> <span class="token punctuation">{</span>
            <span class="token class-name">ExpirationEntry</span> ent <span class="token operator">=</span> <span class="token constant">EXPIRATION_RENEWAL_MAP</span><span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token function">getEntryName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token keyword">if</span> <span class="token punctuation">(</span>ent <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                <span class="token keyword">return</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
            <span class="token class-name">Long</span> threadId <span class="token operator">=</span> ent<span class="token punctuation">.</span><span class="token function">getFirstThreadId</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token keyword">if</span> <span class="token punctuation">(</span>threadId <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                <span class="token keyword">return</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>

            <span class="token class-name">RFuture</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Boolean</span><span class="token punctuation">&gt;</span></span> future <span class="token operator">=</span> <span class="token function">renewExpirationAsync</span><span class="token punctuation">(</span>threadId<span class="token punctuation">)</span><span class="token punctuation">;</span>
            future<span class="token punctuation">.</span><span class="token function">onComplete</span><span class="token punctuation">(</span><span class="token punctuation">(</span>res<span class="token punctuation">,</span> e<span class="token punctuation">)</span> <span class="token operator">-&gt;</span> <span class="token punctuation">{</span>
                <span class="token keyword">if</span> <span class="token punctuation">(</span>e <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                    log<span class="token punctuation">.</span><span class="token function">error</span><span class="token punctuation">(</span><span class="token string">&quot;Can&#39;t update lock &quot;</span> <span class="token operator">+</span> <span class="token function">getRawName</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">&quot; expiration&quot;</span><span class="token punctuation">,</span> e<span class="token punctuation">)</span><span class="token punctuation">;</span>
                    <span class="token constant">EXPIRATION_RENEWAL_MAP</span><span class="token punctuation">.</span><span class="token function">remove</span><span class="token punctuation">(</span><span class="token function">getEntryName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
                    <span class="token keyword">return</span><span class="token punctuation">;</span>
                <span class="token punctuation">}</span>

                <span class="token keyword">if</span> <span class="token punctuation">(</span>res<span class="token punctuation">)</span> <span class="token punctuation">{</span>
                    <span class="token comment">//如果 没有报错，就再次定时延期</span>
                    <span class="token comment">// reschedule itself</span>
                    <span class="token function">renewExpiration</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
                <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
                    <span class="token function">cancelExpirationRenewal</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
                <span class="token punctuation">}</span>
            <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
        <span class="token comment">// 这里我们可以看到定时任务 是 lockWatchdogTimeout 的1/3时间去执行 renewExpirationAsync</span>
    <span class="token punctuation">}</span><span class="token punctuation">,</span> internalLockLeaseTime <span class="token operator">/</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token class-name">TimeUnit</span><span class="token punctuation">.</span><span class="token constant">MILLISECONDS</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

    ee<span class="token punctuation">.</span><span class="token function">setTimeout</span><span class="token punctuation">(</span>task<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>最终<code>scheduleExpirationRenewal</code>会调用到<code>renewExpirationAsync</code>，执行下面这段 lua脚本。他主要判断就是 这个锁是否在redis中存在，如果存在就进行 pexpire 延期</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">protected</span> <span class="token class-name">RFuture</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Boolean</span><span class="token punctuation">&gt;</span></span> <span class="token function">renewExpirationAsync</span><span class="token punctuation">(</span><span class="token keyword">long</span> threadId<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token function">evalWriteAsync</span><span class="token punctuation">(</span><span class="token function">getRawName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token class-name">LongCodec</span><span class="token punctuation">.</span><span class="token constant">INSTANCE</span><span class="token punctuation">,</span> <span class="token class-name">RedisCommands</span><span class="token punctuation">.</span><span class="token constant">EVAL_BOOLEAN</span><span class="token punctuation">,</span>
                          <span class="token string">&quot;if (redis.call(&#39;hexists&#39;, KEYS[1], ARGV[2]) == 1) then &quot;</span> <span class="token operator">+</span>
                          <span class="token string">&quot;redis.call(&#39;pexpire&#39;, KEYS[1], ARGV[1]); &quot;</span> <span class="token operator">+</span>
                          <span class="token string">&quot;return 1; &quot;</span> <span class="token operator">+</span>
                          <span class="token string">&quot;end; &quot;</span> <span class="token operator">+</span>
                          <span class="token string">&quot;return 0;&quot;</span><span class="token punctuation">,</span>
                          <span class="token class-name">Collections</span><span class="token punctuation">.</span><span class="token function">singletonList</span><span class="token punctuation">(</span><span class="token function">getRawName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
                          internalLockLeaseTime<span class="token punctuation">,</span> <span class="token function">getLockName</span><span class="token punctuation">(</span>threadId<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="总结" tabindex="-1"><a class="header-anchor" href="#总结" aria-hidden="true">#</a> 总结</h2><ul><li>watch dog 在当前节点存活时每10s给分布式锁的key续期 30s；</li><li>watch dog 机制启动，且代码中没有释放锁操作时，watch dog 会不断的给锁续期；</li><li>如果程序释放锁操作时因为异常没有被执行，那么锁无法被释放，所以<strong>释放锁操作一定要放到 finally {} 中</strong></li><li><strong>要使 watchLog机制生效 ，lock时 不要设置 过期时间</strong></li><li>watchlog的延时时间 可以由 lockWatchdogTimeout指定默认延时时间，但是不要设置太小。如100</li><li>watchdog 会每 lockWatchdogTimeout/3时间，去延时。</li><li>watchdog 通过 类似netty的 Future功能来实现异步延时</li><li>watchdog 最终还是通过 lua脚本来进行延时</li></ul></div><!--[--><!----><!--]--><footer class="page-meta"><div class="meta-item edit-link"><a href="https://github.com/eddie-lucas/edit/main/src/backend/redis/Redisson看门狗机制.md" rel="noopener noreferrer" target="_blank" aria-label="编辑此页" class="nav-link label"><!--[--><svg xmlns="http://www.w3.org/2000/svg" class="icon edit-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="edit icon"><path d="M430.818 653.65a60.46 60.46 0 0 1-50.96-93.281l71.69-114.012 7.773-10.365L816.038 80.138A60.46 60.46 0 0 1 859.225 62a60.46 60.46 0 0 1 43.186 18.138l43.186 43.186a60.46 60.46 0 0 1 0 86.373L588.879 565.55l-8.637 8.637-117.466 68.234a60.46 60.46 0 0 1-31.958 11.229z"></path><path d="M728.802 962H252.891A190.883 190.883 0 0 1 62.008 771.98V296.934a190.883 190.883 0 0 1 190.883-192.61h267.754a60.46 60.46 0 0 1 0 120.92H252.891a69.962 69.962 0 0 0-69.098 69.099V771.98a69.962 69.962 0 0 0 69.098 69.098h475.911A69.962 69.962 0 0 0 797.9 771.98V503.363a60.46 60.46 0 1 1 120.922 0V771.98A190.883 190.883 0 0 1 728.802 962z"></path></svg><!--]-->编辑此页<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span><!----></a></div><div class="meta-item git-info"><div class="update-time"><span class="label">上次编辑于: </span><!----></div><div class="contributors"><span class="label">贡献者: </span><!--[--><!--[--><span class="contributor" title="email: 761404955@qq.com">Lucas</span><!--]--><!--]--></div></div></footer><nav class="vp-page-nav"><a aria-label="缓存击穿、穿透、雪崩" class="vp-link nav-link prev nav-link prev" href="/backend/redis/%E7%BC%93%E5%AD%98%E5%87%BB%E7%A9%BF%E3%80%81%E7%A9%BF%E9%80%8F%E3%80%81%E9%9B%AA%E5%B4%A9.html"><div class="hint"><span class="arrow start"></span>上一页</div><div class="link"><!---->缓存击穿、穿透、雪崩</div></a><a aria-label="主从复制原理" class="vp-link nav-link next nav-link next" href="/backend/redis/%E4%B8%BB%E4%BB%8E%E5%A4%8D%E5%88%B6%E5%8E%9F%E7%90%86.html"><div class="hint">下一页<span class="arrow end"></span></div><div class="link">主从复制原理<!----></div></a></nav><div id="comment" class="giscus-wrapper input-top" style="display:none;"><div class="loading-icon-wrapper" style="display:flex;align-items:center;justify-content:center;height:96px"><svg xmlns="http://www.w3.org/2000/svg" width="48" height="48" preserveAspectRatio="xMidYMid" viewBox="25 25 50 50"><animateTransform attributeName="transform" type="rotate" dur="2s" keyTimes="0;1" repeatCount="indefinite" values="0;360"></animateTransform><circle cx="50" cy="50" r="20" fill="none" stroke="currentColor" stroke-width="4" stroke-linecap="round"><animate attributeName="stroke-dasharray" dur="1.5s" keyTimes="0;0.5;1" repeatCount="indefinite" values="1,200;90,200;1,200"></animate><animate attributeName="stroke-dashoffset" dur="1.5s" keyTimes="0;0.5;1" repeatCount="indefinite" values="0;-35px;-125px"></animate></circle></svg></div></div><!--[--><!----><!--]--><!--]--></main><!--]--><footer class="vp-footer-wrapper"><div class="vp-footer">记录，分享自己的学习过程.....</div><div class="vp-copyright">Copyright © 2025 小刘Learning</div></footer></div><!--]--><!--]--><!----><!----><!--]--></div>
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